Modelling partial discharge in gaseous voids

Modelling partial discharge in gaseous voids

Modelling partial discharge in gaseous voids

The measurement of partial discharge (PD) activity is a commonly used tool to quantify the health of electrical insulation material in high voltage plant. Models of PD activity have been developed in order to provide insight into the physical conditions present in PD systems. Modern PD models typically use the approach taken in the work of Niemeyer in early 1990's, and so far have been primarily limited to investigating PD activity from simple controlled experiments. PD models have typically focused on PD activity in gaseous voids, which is also the case in this thesis.

In this work a new PD activity model was developed. It addressed several of the shortcomings present in other PD activity models in order to provide a more physically accurate description of PD phenomena and to extend the scope of the model. The model was validated against experimental data in the literature, and was then used to simulate PD activity from a three-phase cable experiment, which is indicative of the more complex PD systems present in operational plant. However, despite this contribution it became evident that many of the assumptions and concepts used in the model, despite having a basis in the literature, have limited justification.

A drift diffusion model was then used to test some of the physical concepts that are employed when modelling PD in voids. The results showed that many of these concepts may be erroneous, with discrepancies between the canonical reasoning and the simulation results. For example, the residual electric field, the electric field after a discharge, is significantly lower than the estimates used by PD activity models in the literature. It is concluded that in their current form PD activity models may not be t for purpose, and it is suggested that a new approach to modelling PD activity is required moving forward.

Abstract

The measurement of partial discharge (PD) activity is a commonly used tool to quantify the health of electrical insulation material in high voltage plant. Models of PD activity have been developed in order to provide insight into the physical conditions present in PD systems. Modern PD models typically use the approach taken in the work of Niemeyer in early 1990's, and so far have been primarily limited to investigating PD activity from simple controlled experiments. PD models have typically focused on PD activity in gaseous voids, which is also the case in this thesis.

In this work a new PD activity model was developed. It addressed several of the shortcomings present in other PD activity models in order to provide a more physically accurate description of PD phenomena and to extend the scope of the model. The model was validated against experimental data in the literature, and was then used to simulate PD activity from a three-phase cable experiment, which is indicative of the more complex PD systems present in operational plant. However, despite this contribution it became evident that many of the assumptions and concepts used in the model, despite having a basis in the literature, have limited justification.

A drift diffusion model was then used to test some of the physical concepts that are employed when modelling PD in voids. The results showed that many of these concepts may be erroneous, with discrepancies between the canonical reasoning and the simulation results. For example, the residual electric field, the electric field after a discharge, is significantly lower than the estimates used by PD activity models in the literature. It is concluded that in their current form PD activity models may not be t for purpose, and it is suggested that a new approach to modelling PD activity is required moving forward.